Sorry if this has already been reported (couldn't find anything in the search). When selecting the warmup length in a dedicated server, it always puts one value higher than you selected. E.g. you put 10 mins, then the server and multiplayer file take the next possible selection by putting 15 mins. The next time you go through the settings it will show 15 mins and when you load the track it goes to 20 mins, and so on.
I have noticed this as well, it just seems to increment to the next time step each time the dedi is started and possibly on each track change but i have not checked the track change to confirm.
There is already a thread about this. We came to the same conclusion: http://isiforums.net/f/showthread.php/3754-Server-Session-Time-Period-Changes
